Hi there,

I have some data formated as below

7:00 15:00
7:00 15:00
8:00 16:00

7:00 15:00
7:00 15:00
6:30 14:30

7:00 15:00

10:00 18:00
11:00 19:00
11:00 19:00



11:00 19:00
11:00 19:00
13:00 21:00
15:00 23:00
15:00 23:00
15:00 23:00


I need to figure out a formula to count how many people would be here at

07:00
08:00
09:00

etc I have been playing around with a few things but so far I have only been able to count up the occurences of people coming in, I can't figure out how to back out the time once people leave.

Can anyone help?